Business confidence among Japan's largest manufacturers is at its lowest since Tokyo introduced measures to kick-start the struggling economy more than three years ago, a central bank survey showed Monday.

Japan's exports tumbled and the country logged a surprise trade deficit in August, data showed Wednesday, reviving concerns about the economy just before the Bank of Japan wraps up a closely watched meeting.

With the merger of FamilyMart Co. and Uny Group Holdings Co. on Sept. 1, the integrated convenience store is now competing as one of the "big three" alongside Seven-Eleven Japan Co., Japan's largest chain, and Lawson, Inc.